don't look to hard... also I don't know why you wan tit becasue it isn't very secure.
<HTML>
<HEAD>
<TITLE>My Page</TITLE>
<SCRIPT language="JavaScript">
<!--- Hide from tired old browsers
/************************************************
Gate Keeper v2.0 by Joe Barta
Get your very own Gatekeeper from Professional Web Design
http://junior.apk.net/~jbarta/weblinks/gate_keeper/
************************************************/
function gateKeeper() {
var password = prompt("Password required:", "")
var location=password + ".html";
this.location.href = location;
}
// done hiding --->
</SCRIPT>
</HEAD>
<BODY BGCOLOR="#FFFFFF">
<A HREF="javascript:gateKeeper()">Click here</A> for some cool stuff!
</BODY>
</HTML>